Light trucks, such as pick up trucks, are typically used for hauling a wide variety of cargoes. Although the cargo bed of such trucks are designed to have the center-of-gravity of the cargo optimally located in the center of the bed to provide for uniform loading on the axles of the truck, sometimes an item of cargo has a significantly non-uniform weight distribution which can prevent this from being realized. In some of these cases, such load imbalances can create performance and safety problems in the operation of the vehicle. Further, the suspension of such vehicles are designed for a fully-loaded truck, and an unloaded truck can at times have insufficient weight to allow for good traction in slippery road conditions.
In addition, much of the prior art does not provide a secure attachment of the ballast to the truck. Emergency braking, and collisions can cause severe safety problems when such ballast becomes dislodged while the truck is under way.
Several approaches have been proposed for overcoming both the traction problem and the weight distribution problem through the use of additional ballast being added to the cargo area. Most such approaches involve the use of hollow containers which when filled with a liquid or a granular material, such as sand, provide the additional weight as it is needed. When the weight is not needed, a drain is provided to remove the filler material.
Some of these approaches fit within the wheel-well cavity areas as vertical-standing containers such as that disclosed in U.S. Pat. No. 4,190,281 to Chandler. Distribution over the cargo bed of such containers allows for both counterbalancing a non-uniform cargo and to provide the additional traction weight for the road condition problem. A principal drawback in the use of such containers is that areas that would normally be used for cargo are occupied by the ballast containers.
To overcome this inefficient use of cargo space, systems have been proposed that incorporate shallow, flat fill-able cavities that cover the entire surface of the cargo bed, such as in the teachings of U.S. Pat. Nos. 4,796,914 to Raynor and 5,330,227 to Anderson. Raynor discloses a conformal shell that fits to the entire inside of a pickup bed cavity, and has a shallow hollow at the bottom of the shell for filling with a liquid to provide a uniform weight over the entire cargo bed. A drain valve is provided for removing the liquid when not needed. This provides a solution to the traction problems, but provides no relief to the weight distribution problem.
Anderson teaches a plurality of rectangular hollow beams that are laterally arranged to provide the "full-bed" coverage for the traction problem, but has the ability to remove one or more of the beams to accommodate the needs of a load distribution, although in a limited manner. The fill material is non-liquid, and can be inserted and removed through a removable end-cap. A bolted retaining bar secures the beams in place to the bed of the truck by interlocking with the end cap to prevent bouncing and movement of the ballast beams. A significant drawback is that counterbalancing weight cannot exceed that of a few filled beams. A further disadvantage is that the use of the non-liquid filler material creates a more difficult removal and storage issue over those using a liquid filler material and can be filled with a conventional hose.
To overcome the above drawbacks, the present invention provides for a plurality of fill-able interlocking plank-like hollow ballast containers that are secured to the truck bed. When interlocked laterally across the truck bed, such containers provide a solution to the traction problem. When stacked and secured vertically, the containers provide selective weight distribution for counterbalancing requirements. Further, the present invention provides a means for the easy removal of excess weight when it is no longer needed through either the removal of individual ballast elements or through the selective draining of the filler material.